1. Technical Field of the Invention
The present invention relates generally to a collision detection apparatus working to detect a mechanical impact more than a preset level upon an accidental vehicle collision, and more particularly to an improved structure of such a collision detection apparatus designed to minimize contact chatter in the apparatus.
2. Background Art
Japanese Patent No. 3191724 (U.S. Pat. No. 5,898,144, issued on Apr. 27, 1999, assigned to the same assignee as that of this application) discloses a conventional collision detector which, as shown in FIG. 5, consists of a rotor 3, a first contact spring 7, and a second contact spring 8. The rotor 3 is responsive to an impact arising from a vehicle crash to rotate and urge the first contact spring 7 into contact with the second contact spring 8, thereby producing an electrical signal. The second contact spring 8 is made up of two leaf springs in order to increase an elastic pressure required to secure the stability of contact between the first and second contact springs 7 and 8 without contact chatter.
Usually, most of vehicle collision detectors are installed in a front portion of a vehicle body (e.g., a front fender) for the purpose of early detection of a vehicle collision. Specifically, the vehicle collision detectors are placed in an environmental condition where they undergo a great deceleration and still have a difficulty in eliminating the contact chatter completely.
It is therefore a principal object of the invention to avoid the disadvantages of the prior art.
It is another object of the invention to provide a collision detecting apparatus which is designed to secure the stability of an electrical contact in the apparatus without any contact chatter.
According to one aspect of the invention, there is provided a collision detecting apparatus which may be employed in actuating a safety restraint system such as an air bag upon a vehicle crash. The collision detecting apparatus comprises: (a) a moving member moving when subjected to an impact of more than a given level arising from a collision with another object; and (b) a first and a second contact member which are disposed on a mount base and extend with a given gap therebetween. The first contact member is brought by the moving member into contact with the second contact member to produce an electrical signal indicative thereof when the moving member undergoes the impact of more than the given level. At least one of the first and second contact members is made of a leaf spring which has a length including a base portion secured on the mount base and a contact portion for establishing a contact with the other of the first and second contact members. The base portion is larger in width than the contact portion. This results in a decrease in weight of the contact portion, so that the contact portion remote from the mount base is less susceptible to vibrations to avoid contact chatter.
In the preferred mode of the invention, the at least one of the first and second contact members is decreased in width gradually from the base portion to the contact portion.
At least one of the first and second contact members may alternatively be decreased in width in a stepwise fashion from the base portion to the contact portion.
The leaf spring may have a reinforcement rib formed thereon to compensate for a loss in rigidity resulting from the decrease in width of the contact portion.
The second contact member is made up of a first and a second leaf spring. The first leaf spring works to establish the contact with the first contact member when pressed by the moving member. The second leaf spring works to produce an elastic pressure to urge the first leaf spring against the first contact member when the first contact member is pressed by the moving member and makes the contact with the second contact member.
A first point of the contact of the first contact member with the second contact member established by the moving member and a second point of contact of the moving member with the first contact member may be located at the same interval away from the mount base. In other words, the first point may coincide spatially with the second point. When brought into contact with the second contact member, the first contact member is pressed by the moving member on the first point, thereby suppressing mechanical vibrations of the first contact member on the first point to avoid the contact chatter.